Process of making tanning extracts.



ROBERTO LEPETIT AND ERNESTO TAGLIANL OF SUSA, ITALY.

PROCESS OF MAKING TANNING EXTRACTS.

Specification of Letters Patent.

Patented Sept. 12, 1905.

Original application filed July 16, 1896, Serial No. 599,718. Dividedand this application filed March 18,1902. Serial No. 98,828. (Specimens)To (LU whom it Hm/, cancer/1 Be it known that we, ROBERTO Luru'rrr,chemical manufacturer, of Susa, in the Kingdom of Italy, and ERNESTOTAGLIANI, technical chemist, of Lugano, Confederation ofSwitzerlanchboth residing in Susa, Italy, have invented an ImprovedTanning Material and Process of Producing the Same, of which thefollowing is a specification.

This application is a division of our application Serial No. 599,718,filed July 16, 1896.

Our invention consistsin the production of a tanning extract containingthe tanning principles of tan-woods and which extracts are readilysoluble in cold water, forming clear solutions.

It is well known that certain extracts produced from tan-woods such, forinstance, as from quebracho-wood, hemlock, and similar woods-contain thetanning principles in a difficultly-soluble resinous condition whichrenders their application in the tanning industry disadvantageous.

It is the object of the present invention to produce such tanningextracts in a condition readily soluble even in cold water, and therebyto render the valuable and important tanning principles containedtherein available in the tanning art.

It has been known for a considerable period of time that woods of thecharacter mentioned, particularly quebracho-wood, contain valuabletanning principles and have been employed in tanningon that account.\Vhere the wood itself has been used by the tanner, extracts have beenobtained therefromin the ordinary manner generally followed in thetanning industry; but these extracts have resulted only in obtaining themore soluble principles, and the most valuable of the tanningconstituents being of a resinous glutinous insoluble character haveeither not been extracted at all or only to a very small extent. It hasbeen known that the entire tanning constituents of such woods mayextracted by boiling under pressure; but extracts so obtained are of aglutinous or resinous character at ordinary temperatures and are onlyvery difticultly soluble in cold water, such solutions being generallyof a turbid or cloudy character.

It is the object of our invention to convert such extracts into extractscontaining all the valuable constituents of the wood in a condition inwhich they are readily soluble in cold water, giving clear solutions.

While our invention as herein described is applied to the extractsthemselves, it will be readily understood that the invention may also beapplied,with more or less satisfactory results, to the wood from whichthe extracts are obtained.

Our invention consists in treating either the extracts themselves or thewoods from which they are obtained with a salt of sulfurous acid. Theparticular salts which we prefer to employ are the sullites, bisullites,or hydrosullites of the alkali metals, such as sodium suliite, sodiumbisulfitc, or sodium hydrosullite. Any of the corresponding sulfurousacid salts of potassium or ammonium may be employed, if desired. \Vhenacid salts, such as the bisullites, are employed, the reaction requiresa temperature of 100 centigrade and above, and hence requires to beconducted in a closed vessel under pressure. \Vhen, however, neutralsalts, such as the sullites, are employed, the heat required does notexceed 100 centigrade, and hence the process may be performed in an openvessel without pressure.

In order to make a complete disclosure of our invention and to enableothers skilled in the art to perform the same, we give below specificexamples.

Example I: For the manufacture of a quebracho extract readily soluble incold water from the ordinary difiicultly-soluble quebracho extract:

a. Three hundred kilograms of quebracho extract of Baume are mixed witheighty kilograms of bisullitc of soda of 35 Baum and heated in a closedvessel at 130 to 145 Centigrade during eight hours.

The product obtained differs from the usual quebracho extracts by itsperfect solubility even in cold water and by its property of giving asofter pale nicely-pink-colored leather very similar to hides tannedwith mimosa bark. An important property of our soluble extract is thatit penetrates more rapidly into the pores of hide than usually lesssoluble quebracho extract.

6. Five hundred kilograms of quebracho extract, one hundred. and twentykilograms of bisnllite of soda at 115* Baunu': or of a solution ofsullite of soda of 30 Baume or one hundred and eighty kilograms ofhydrosullite of soda of Baum are treated for from eight to ten hours inan open copper vessel with a double bottom heated by steam and providedwith an agitator until a sample taken from the mass is easily soluble incold water.

0. Soluble qucbracho extracts may also be obtained by extracting thequebracho-wood in presence of bisulfite or sultite of soda for instance,by boiling under or without pressure one thousand kilograms ofquebracho-wood with water to which has been added one hundred and ten toone hundred and thirty kilograms of bisulfite of soda (35 Baum) orcrystallized neutral sultite of soda and evaporating the decoction untilit tests 25 to 30 Bauni.

In every case, working as at ab 0, the extract is perfectly soluble incold water and tans quicker than the quebracho extracts generally known.The leather becomes softer and of a much paler color of a pleasant pinkshade. The palest product is obtained as described at a.

Example II: For the manufacture of a hemlock extract readily soluble incold water from usual hemlock extract:

The ordinary hemlock extracts (which are difricultly soluble in coldwater) are changed into soluble extracts by the same processes as usedfor quebracho extractsthat is to say, working as described at a and b ofExample I. The hemlock extract thus treated dissolves readily in coldwater and has to usual hemlock extracts comparatively the sameadvantages as soluble quebracho has to usual quebracho.

The weights and temperatures mentioned in our description may bealtered, of course, to some extent, and sulfites, bisulfites, andhydrosulfites of potash and of ammonia may be used instead of the sodiumsalts.

The reaction by which the diificultly-soluble extracts are convertedinto a readily-soluble condition is dependent upon the amount of sulfiteand bisulfite employed and the heat under which the reaction isconductedthat is to say, that with equal additions of bisulfite theextent of the reaction increases on an average with the temperature andthat at equal temperatures the extent of the reaction increases as theamounts of sulfite or bisulfite employed and also that the extent of thereaction is dependent to a certain extent upon the time of duration ofthe same. For instance, after a period of, say, six hours duration thereis very little further change noted after a period of eight hoursduration.

By the above-described treatment with a salt of sulfurous acid underheat and pressure resinous and comparatively insoluble tanning extractsare converted into soluble extracts containing resinates of the soda orother base used.

Leather tanned with our improved extracts is characterized by itsclearer color and greater pliability than that obtained with theordinary extracts, while at the same time its pores are not filled withforeign matter and impurities present in the ordinary extracts.

The great solubility imparted as a result of our process appears,according to investigations made upon the extracts, to be due to thepresence of chemically-combined sulfur as a sulfonic group, (SOSPL)which is not eliminated by heating the extract with sulfurous acid.

Having thus described our invention, the following is what we claim asnew therein and desire to secure by Letters Patent:

1. The process of treating tan-wood extracts of the character describedwhich consists in heating said extracts with a salt of sulfurous acid ina manner and to an extent to cause the tanning principles of theextracts to combine with the acid constituent of the salt to produce anextract readily soluble in water.

2. The process of treating extract of quebracho-wood to produce atanning'extract which consists in heating said extract with a salt ofsulfurous acid in a manner and to an extent to cause the tanningprinciples of the extract to combine with the acid constituent of thesalt to produce an extract readily soluble in water.

3. The process of treating extracts of quebracho-wood to produce atanning extract soluble in water, said process consisting in heatingsaid extracts with a salt of sulfurous acid at a temperature of 100centigrade and above for the period of from six to eight hours.

L. A tanning extract readily soluble in cold water and giving a clearsolution therewith and containing chemically-combined sulfur.

5. An extract of quebracho for tanning, said extract containing thenormally resinous and diflicultly-soluble constituents in a conditionsoluble in cold water. I

6. A tanning extract containing the tanning constituents ofquebracho-wood, said extract readily soluble in cold water giving aclear solution therewith and containing chemically-combined sulfur.

7. A tanning extract consisting in the product of the reaction of asulfite or bisulfite upon a normally resinous and difficultly-solubletan-wood extract said product being readily soluble in cold water andcontaining chemically-combined sulfur.

ROBERTO LEPETIT. ERNESTO TAGLIANI.

Witnesses:

HENRY OPYZoTE, CLEMENTE GINEZETTL

